Lindetorpsvägen 7, Stockholm, Sweden
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Nypol is a group of polymer modified binders that provide enhanced resistance to rutting, deformation, cracking and wear, making them ideal for surfaces that are subjected to heavy loads.
Traffic on the E20 approaching Gothenburg from the west gets busier the nearer you get to the city. An average of 50,000 vehicles use this section every day, 10% consisting of heavy goods vehicles. The condition of certain sections of the road has worsened in recent years. This is partly due to a porous asphalt surfacing whose open structure can age more quickly because of exposure to water and air. The problems on the E20 were evident in particular along a 5km section of primarily three lane highway.
Aiming to achieve a long term solution, the Swedish Transport Administration decided to mill off the entire surface course of this section plus some of the underlying binder layer. A total review of the road’s geometry was conducted at the same time in order to correct lane gradients and adjust for subsidence.
A computer generated model of the road was entered into the milling machine’s control equipment. By calculating the position of the machine using total stations, the milling depth could automatically be adjusted according to the model. The gradient between the lanes was thereby precisely secured, an essential prerequisite for use of a widened asphalt paver to lay two or more lanes simultaneously.
The whole section was refurbished in two layers because of the depth of the original material removed. Polymer modified binder (PMB) was used in both the binder layer (50 mm) and surface course (30 mm) to meet tough demands for stability and fatigue resistance. The choice of PMB – Nypol 67 and Nypol 73 from Nynas – means that the estimated lifespan of the refurbished carriageway has been increased compared with a conventional surfacing. A total of approximately 20,000t of polymer modified asphalt was used to complete the project.
Roadworks and other disruption to the section of E20 being refurbished could have had an impact to varying degrees on other traffic in and around Gothenburg. Temporary lane changes were made at night time to minimise any restrictions to accessibility and also to increase employee safety; these changes were then reversed to ensure normal traffic running in the morning.
The minimum requirement from the client was that two lanes should be laid in parallel as it was deemed the tight schedule could not otherwise be met. In the event, the contractor chose to lay the three lanes simultaneously to speed the project and also earn a bonus. One widened paver was used to lay two lanes with a supplementary machine operated in tandem to lay the third lane. This had the added advantage of minimising the number of transverse and longitudinal joints in the carriageway surfacing.
LOCATION E20 Gothenburg, Sweden
ASSIGNMENT New binder and surface course
CLIENT Swedish Transport Administration
DATE Summer 2016